Baffle height calculations

[BC Mosaic]

How do you calculate how high your baffles should be in a sump?
Is there a formula?
This is the only thing (besides a top off system) that I need to get done so that i can start running my refugium and skimmer/sump.
Thanks and I appreciate the help.

[Captainhemo]

Your baffle height will determine the waer level in the chamber preceeding the baffles.

[sphelps]

Yes and you should also plan for optimal skimmer water levels and allow enough extra volume to handle back flow. I usually allow 2" from the display for a minimum and go from there. For example a 90 gallon has a 48x18 foot print meaning 2" of water equals 1728 cubic inches. That means with a sump foot print of say 36 x 12 you'll need 4 inches. However the next step would be to decide on an additional factor of safety, for example a SF of 2 would mean you need 8" of free height in the sump. That may be a bit extreme but you get the idea.

You should also consider the display tank size. A common mistake in my opinion is when people add too much volume with their sump. Any display 90 gallons or more has plenty volume for stability and extra water volume has little benefit. Therefore for efficiency reasons you should minimize sump volume, especially easy if you have an ATO.

I would be happy to make some more specific recommendations if you could give more information regarding display and sump size, as well as equipment used.

[BC Mosaic]

Thanks sphelps.
I've been racking my brain for the past 2 weeks about this and my head is starting to hurt!

My reef tank is an 80g rimless with a foot print of 48" x 16" and it is not drilled.Because I don’t have the room to house anything under the tank, the sump & refugium will be installed off to one end of the tank. Top of the tank is at 5'.

I picked up an acrylic refugium which is made out of ¼” thick acrylic except for the end pieces which are 3/8”thick. The overall (outside) dimension is 32” long x 14 ¼” high x 14 3/8’ deep. The spaces between the baffles are 4 3/8”, 3 1/16”, 2 7/8”. That leaves an open space of 20 3/8” for cheato + LR (maybe a sand bed as well ?). There is also a 1 1/2" bulkhead whose center is up 3 1/2" from the inside bottom at the baffle end.

Tomorrow I hope to be picking up an industrial shelving unit that is more than strong enough to support this refugium above the main tank at 5 feet and so the refugium will just empty itself after the baffles directly into the tank. Underneath the refugium is where I'll house the sump which is a regular 33g glass tank (36" x 12" x 18") and here is where I got stumped with the height of the baffles. The out flow from the tank to this sump will be a surface skimmer with dual 1 1/4" OD u-tubes with flexible hoses. The main skimmer is 19" tall to the bottom of the collection cup with a diameter of 7". I plan on raising it 3 3/8" with white PVC pipe support and eggcrate (was suggested I do this). The skimmer's footprint is 12" x 12" (approx.) which leaves another 2' of room in this tank (for LR ?) plus the baffles. I mention LR for both sump and refugium because I have an excess of it. Here is a photo of the skimmer:

The pump from the sump to the refugium will be a Rio 2500.Here is a drawing of what I think the whole set up should be (not to scale):

So, Have I figured this out properly? Besides not knowing the height of the baffles in the sump am I still misssing something (besides an ATO which will be next right after I install a tunze wavemaker )?

Thanks for your time and effort.
Cheers

Richard
BC Mosaic